Streptococcus pyogenes, the group A streptococcus (GAS) is an important human pathogen causing frequent self-limiting diseases which may lead to serious sequelae. In addition, the GAS seems to be "re-emerging" as an important pathogen which causes life-threatening invasive disease. We will continue to use molecular genetic approaches to obtain a better understanding of known and presumed virulence factors of GAS and to identify new ones and to elucidate their regulation.